Elongated doctor blades which have flexibility transverse to their longitudinal direction are known in the art, see, for example, German Patent Disclosure Document DE-OS No. 25 45 737 and U.S. Pat. No. 2,283,830.
The doctor blade is subdivided into regions or zones by grooves formed therein which extend parallel to each other. The structure described in the German Disclosure Document DE-OS No. 25 45 737 has groove-like recesses with semicircular cross-section. The structure described in this U.S. Pat. No. 2,283,830 has grooves with a square, or, alternatively, triangular cross-section.
It has been found that neither of the solutions proposed in the above publications ensure that application of a certain zone of the doctor blade to the duct roller will result in specific independent adjustment without affecting adjacent zones; rather, positioning of a certain zone of the doctor blade with respect to the duct roller influences adjacent zones. Consequently, it is difficult to arrange the ink supply in clearly defined zones with definite widths without overlap, or drawing over the edge of the adjacent zone.